As a waste heat utilization device for an internal combustion engine, a cooling device for an automotive internal combustion engine is disclosed. This cooling device constitutes a Rankine cycle circuit including an evaporator, an expander and a condenser serially arranged in a circulation line along which CFC as a working fluid (hereinafter referred to as “refrigerant”) circulates, where heat is transferred from automotive engine cooling water to CFC in the evaporator. Drive power produced by the expander drives a radiator fan provided to the condenser, and CFC condensed in the condenser cools the engine (see Japanese Patent Application KOKAI Publication Sho 61-155614).
At present, in order to prevent ozone layer depletion, alternatives for CFC, such as R134a, are used as refrigerants for such cooling devices. Such alternatives for CFC have, however, a very high GWP (Global Warming Potential), so that there still exists a concern about their environmental impact.
To cope with this problem, it is conceivable to use a hydrocarbon-based natural refrigerant in the aforementioned conventional technology. The hydrocarbon-based refrigerant is however combustible. If this refrigerant leaks from the circulation line, the evaporator, the expander or the like, it may possibly ignite, or at worst, explode.
Further, the aforementioned conventional technology, in which the radiator fan provided to the condenser is driven by drive power produced by the expander, has a problem that malfunction of the Rankine cycle circuit due to some reason or a reduction in drive power produced by the expander results in insufficient cooling of the engine.